1. Field of the Invention
The present invention relates generally to a building energy management method and system and, more specifically to a novel natural ventilation and waste heat recovery system.
2. Description of the Related Art
Solar heat continually builds up in walls and attic space during the summer season as a result of the sun's rays penetrating walls and roofing materials on buildings. Temperatures in attic spaces can rise to 130 degrees and higher as a result of solar heat. The sun's heat is continually penetrating the exposed exterior surface of every building. To date, builders and architects have attempted to combat the problem by using more insulation or insulation with a higher “R” (resistance) factor and/or larger and more expensive mechanical equipment. Home and building owners ultimately pay the price in terms of higher materials costs to build the home or building and in terms of higher utility bills. Yet, it is far more expensive and difficult to deal with cooling heated air after it enters the cooled interior space than to prevent the heat from ever entering the space at all.
Heat transfer is the movement of heat from one place to another. The laws of thermodynamics govern heat transfer and it is a scientifically accepted principle that heat travels to cold. In other words, as the sun beats down on roofs and walls, the heat radiates through the structure and is trapped in the attic spaces and within the building, which is typically a lower temperature than the outdoors.
The trapping of solar heat in attic spaces is a well known problem and one method of addressing it is by attic ventilation fans, which help the hot air to release to the outdoors. Although a somewhat effective solution, attic fans only partially release the trapped heat in the attic space and do not address the heat trapped in the wall spaces. Energy recovery ventilation systems transfer heat from outgoing air to incoming air in the winter, and from incoming air to outgoing air in the summer, leading to lower heating and cooling requirements. There are several different types of energy recovery ventilation systems, but they all have in common a heat exchanger, controls, and one or more fans to move air through the machine. Although effective with regard to providing significant energy savings in heating and cooling, energy recovery ventilation systems are somewhat expensive to install, require maintenance and require electricity to run. These systems provide the most return on investment in climates with relatively extreme season or where costs of heating and cooling are unusually high.
Historically, buildings inherently had an abundance of natural ventilation by means of naturally occurring gaps and air spaces. As construction processes have improved, structures are much more air-tight than they once were, and as a result now rely on artificial heating and cooling, resulting in high energy costs. Natural ventilation systems rely on pressure differences to move fresh air through buildings. Pressure differences are caused by wind, the buoyancy effect created by temperature differences or differences in humidity. Regardless of the triggering factor, the amount of ventilation depends on the size and placement of openings in the structure.
A natural ventilation system really is a circuit, with equal consideration given to supply and exhaust. Openings such as transom windows, louvers, grills, or open floor plans are traditional ways one can complete the airflow circuit through a building.
One must also take into account code requirements regarding smoke and fire transfer when designing a natural ventilation system. For example, older buildings once used the stairway as the exhaust stack, which is no longer allowed due to code requirements.
Due to the above described difficulties, it is a challenge to design a ventilation system that is conducive to artificial heating and cooling yet simultaneously reduces energy costs by maximizing natural ventilation.
U.S. Pat. No. 3,368,473 describes construction panels and prefabricated structural members designed to create a ventilation section and an insulation section, the ventilation section to remove and prohibit the communication of solar heat to the interior of the building. The patent describes use of insulating material bounded by sheets on either side, the sheets formed in overlapping sections.
U.S. Pat. No. 4,677,903 describes supplementary building construction to be added to the roof and/or external walls of an existing building structure to selectively create air flow over external surfaces of the building or to alternatively trap air as needed to assist with unwanted heat absorption. The invention describes the necessity of covering flaps for the open ends of the air space.
U.S. Pat. No. 6,319,115 describes air cycle houses and house ventilation systems and has insulating and ventilating layers. This invention draws outdoor air into the indoor space from an air intake and further utilizes a heat exchange ventilator.
Although the prior art patents described above discuss innovative methods for using natural ventilation or heat exchange ventilation to improve energy costs, none disclose an inner wall construction design and solar energy intercept and waste heat recovery system such as described herein, wherein unwanted heat is diverted outside during the summer, before it ever enters the cooled interior space, and is diverted inside during the winter for use to assist with heating the interior space.